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Key to Dioscorea

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1 Leaves with a slightly to strongly concave section at the transition from the basal lobes to the terminal portion of the leaf; leaves alternate, opposite, or a mixture of alternate and opposite.
..2 Leaf apex mucronate or acuminate; leaf lateral lobe apices rounded; petiole base not clasping; leaves 3-9 cm wide
1 Leaves with continuously convex lateral margins (except just below the acute to acuminate leaf apex) or with slight undulations of straight to very slightly concave sections.
....3 Aerial tubers never present; perennial from rhizomes < 1.5 cm in diameter; leaves whorled, alternate, or a mixture of whorled and alternate; [native species, usually of forests and woodlands]; [section Macropoda].
......4 Leaves with 7 main veins; staminate inflorescences usually of 1 large and 1-2 smaller secondary panicles in each axil (of upper stem leaves); filaments inwardly curved, ca. 0.4 mm long; anther lobes connate; tepals oblong; leaf margins often with subtle, very broad lobes, the margin thus with straight or very slightly concave segments; [of SC south]
......4 Leaves with 9 or more main veins; staminate inflorescence a single panicle in each axil (of median or upper leaves); filaments straight, ca. 0.2 mm long; anther lobes separate; tepals ovate; leaf margins convex; [widespread in our area]
....3 Aerial tubers present; perennial from large, vertically-oriented tubers; leaves alternate, or a mixture of alternate and opposite; [non-native species, usually in disturbed areas, especially in bottomlands]; [section Enantiophyllum].
........5 Stems with 2-4 wings or angles (these often purplish); leaves alternate below, opposite and decussate above; aerial tubers dark-brown and elongate; stem twining from left to right (dextrorse; looking from below, the stem turns clockwise)
........5 Stems terete; leaves alternate; aerial tubers tan to light brown, usually globose; stem twining from right to left (sinistrorse; looking from below, the stem turns counterclockwise)
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